The suspects have been identified as Keith Esters and Johnathan Perkins, and police said the motive was attempted robbery.

Boken, 23, was a former volleyball star at St. Louis University who was in town to play a match that pitted alumni against student athletes. She was shot to death while sitting in her Volkswagen on Saturday afternoon, hours before the game, police said.

A police report released today by St. Louis circuit attorney Jennifer Joyce's office reveals how police solved the crime.

"Investigation into the shooting led to a cell phone that was connected to another robbery that occurred in that area," Office Jerone Jackson wrote in his police report. "That investigation led to a witness who stated that her boyfriend, Keith Esters, admitted to her that he was involved in the shooting of Ms. Boken."

The woman told police that Esters and his cousin, Perkins, planned to drive to the area and commit the robbery.

When police contacted Perkins, he said that he had agreed to drive Esters to the robbery and that when Esters spotted Boken sitting in her car talking on her cell phone, Esters said that she would be the target of the robbery.

Perkins allegedly stopped the car and Esters got out to commit the robbery. Esters allegedly shot Boken twice and told Perkins he had done so, and the two left the scene.

Esters has been charged with first degree murder, first degree attempted robbery and two counts of armed criminal action. Perkins was charged with second degree murder, second degree attempted robbery and two counts of armed criminal action.

Both men were arrested on Thursday and are being held without bond.

The arrests happened as hundreds of family and friends gathered in the west Chicago suburb of Wheton for Boken's funeral.

"We are gratified with the progress they've made in the case," he said via telephone. "It was a very difficult day today, but with all the people there for us, it helped us get through it."

Boken graduated with a degree in business administration with a concentration in marketing from St. Louis University in 2011.

She was wounded in the neck and chest, and pronounced dead at Barnes-Jewish Hospital.

"We have no evidence that she knew [the gunman]," he said.

Mayor Francis Slay said Boken's death made him feel "angry and frustrated and determined."

"I am frustrated because American cities, including ours, are awash in guns. Crime has trended down in St. Louis for the past six years in almost every category except gun violence," Slay wrote on his blog.